The invention relates to an apparatus for stacking sheets, in particular overlapping and moving paper or cardboard sheets onto pallets, having a vertically fixed but height-adjustable conveyor above the maximum stack height with a raisable and lowerable deposition platform on which the stacks are formed and a row of upper belts that extend from the conveyor at least into the stacking station and that coact with further stack-forming elements that are effective on the longitudinal edges of the sheets, the upper belts and the further stack-forming elements being positionable along the working width by means of an adjustment device.
Apparatuses for transversely cutting paper or cardboard webs normally end at a stacking apparatus where the sheets produced by transverse cutting are deposited with their edges aligned in stacks. Normally the sheets are transported in overlapping condition by a belt conveyor to the stacking station where they are stacked on pallets that sit on a deposition platform. The deposition platform can be raised in the frame of the stacking machine to the level of the conveyor plane and can be dropped down to the floor. One or more stacks are formed on the deposition platform in case the paper or cardboard web has been cut into several strips prior to transverse subdivision.
At the end of the conveyor and in the stacking station there are known stack-forming elements that ensure a trouble-free guiding in the stacking station and good edge alignment in the stack or stacks. When the format and/or the number of stacks changes the stack-forming elements must be repositioned both transverse to the sheet-travel direction and in the sheet-travel direction since their desired position is dependent on the length and/or width of the sheets being deposited.
The stack-forming elements must all be positioned transversely as they act on the longitudinal sheet edges or must be moved out of the sheet-edge regions since they would there interfere with the operation of the active elements. The elements working on the longitudinal sheet edges are separating shoes that are arranged at the end of the conveyor and that impart to each sheet a shape-stabilizing curved shape and in a multiple-line operation ensure a separate guiding of two adjacent sheets in the stacking station. Furthermore there is at each longitudinal edge of each stack being formed in the stacking station an upright separating plate extending in the sheet-travel direction and engaging the longitudinal edge of the respective stack. Normally the separating plates are vibrated in order to ensure the proper edge alignment of the sheets in a stack.
Further transversely positionable stack-forming elements are feed rollers and upper belts that preferably are arranged at uniform transverse spacings above the stacking station. The feed rollers are arranged at spacings in the region of the ends of the conveyor immediately above the feed plane. They ensure the transfer of the sheets from the conveyor into the stacking station. In order to guide the sheets also in the stacking station, above the conveyor plane are several upper belts extending in the transport direction at least into the stacking station and arranged at a spacing from one another. A stacking apparatus for sensitive paper has its upper belts extending over the entire stacking station. Feed rollers and upper belts are preferably set in a plane. They need in order to accurately transport the sheets not to be too far from each other and not to be set at the longitudinal sheet edges since they would there interfere with operation of the separating shoes and separating plates.
Stack-forming elements whose positions are dependent on the sheet length and that must therefore be positioned longitudinally are one or more stop plates against which the leading edges of the sheets are aligned. At the same time it is also necessary to position the separating plates longitudinally so that they can act on the right position on the longitudinal edges.
German 3,114,414 describes such an apparatus that makes it possible to automatically reset the stack-forming elements when format is changed. To this end the apparatus has a row of entrainment shafts extending in the transport direction, one entrainment shaft carrying two upper belts, two feed rollers, a stop plate and, between the upper belts, a separating shoe and a separating plate. All the stack-forming elements on an entrainment shaft are thus moved together with the entrainment shaft into a new position.
This solution is expensive to manufacture since the number of necessary upper belts is equal to the number of the stack-forming elements effective on the longitudinal edges. Should for example when stacking sensitive papers the spacing between two upper belts be at most 200 mm, with a working width of about 2200 mm, more than ten entrainment shafts for the necessary number of upper belts with the necessary stack-forming elements are necessary. The stack-forming elements only acting on one sheet longitudinal edge (separating shoes, separating plates) whose necessary number is equal to the number of longitudinal edges, thus of the number of adjacent stacks, are set, so a great number must be maintained.
It is therefore an object of the invention to improve on such an apparatus such that it is possible to substantially automatically transversely position the individual stack-forming elements at the lowest possible manufacturing cost.
This object is achieved according to the invention in that the upper belts are adjustable independently of the stack-forming elements effective on the longitudinal edges. This makes it possible to limit the number of stack-forming elements effective on the longitudinal edges of the sheets being stacked to their necessary number (number of users+1).
The raisability of the separating shoes to above the upper belts makes it possible to move them independently of the upper belts and simultaneously therewith into a new transverse position.
In case feed rollers are provided, these are advantageously mounted directly above the active lower reach of the upper belts. Since then their transverse positions correspond o those of the upper belts, they have advantageously a common adjustment mechanism with the upper belts. According to the particularly advantageous embodiment each feed roller is mounted on a holder that also forms a guide for an upper belt. This makes it possible to couple the holder to the adjustment device and thus to move the respective upper belt without its own coupling device during adjustment of the feed roller into its new transverse position. In order to achieve this with the lowest possible manufacturing costs, the circulating upper belts are looped at upstream and downstream ends over rollers extending the full working width. The upper belts thus are easy to slide on the rollers.
According to the invention, a transversely positionable separating plate is provided in the stacking station at each longitudinal edge of a sheet. The separating plates have their own adjustment mechanisms for their transverse positioning. In case the separating plates also have to be positioned longitudinally, this can be done in a simple manner with a separate transverse-adjustment mechanism. If no longitudinal positioning is necessary, the separating plates are coupled to the transverse-adjustment device of the separating shoes since they also act on the longitudinal edges of the sheets.
In order to deposit sensitive paper sheets it is necessary to guide these by means of the upper belts over the entire stacking station. The upper belts reach to this end over the entire stacking station in order to cover the maximum sheet length. On depositing short sheets one must avoid collisions of the leading edges with the stop plates positionable longitudinally. With the described embodiment according to German 3,114,414 the stop plate is formed as a row of short segments that must jointly be positioned transversely with the upper belts.
According to a particularly advantageous embodiment of a stacking apparatus a one-piece stop plate is used so that transverse positioning of separate stop plates is not necessary. Transverse adjustment of the upper belts is still possible since these can only assume predetermined transversely spaced positions. Collisions with the one-piece stop plate are thus avoided in that it has cutouts in all possible transverse positions of the upper belts through which same pass.
The stop plates can be moved out of the region of the upper belts so same can be transversely positioned. This is much simpler than moving them longitudinally from the region of the upper belts. In an advantageous embodiment of the adjustment device for transverse positioning, an absolute-measuring position-detecting system makes it possible to directly control the individual desired positions.